Coupling



FIG. 1 is a top plan view of a coupling showing our new design;

FIG. 2 is a side elevational view thereof, the opposite side being a mirror image of the side shown;

FIG. 3 is an end elevational view thereof, the opposite end being a mirror image of the end shown; and

FIG. 4 is a bottom plan view thereof. 

The ornamental design for a coupling, as shown and described. 